"There have been studies, the results range from a low of 28 percent to nearly 50 percent of U.S. pets are overweight," veterinarian David Carey, who works on research and development for IAMS, the pet food company in Dayton, Ohio, told UPI's Animal Health. "When one asks practicing veterinarians, they say closer to 50 percent or 60 percent."

Yes, pets seem to reflect the lifestyle of their owners, especially the coach potatoes.

"It has been long known that an overweight owner is twice as likely to have an overweight pet as a non-overweight owner," Carey said. "With the report earlier this year that those in the United States are 60 percent overweight/obese, it makes sense that we would see a similar high number for their dogs."

Unfortunately, being overweight has many of the same consequences for pets as it does in humans, including increasing heart disease and diabetes.

"Being overweight can and will decrease the lifespan and lower the quality of life of a pet," Nancy Irlbeck, Colorado State University College of Veterinary Medicine in Fort Collins, told UPI. "Structurally the body suffers with the added weight and we see the increase of arthritis and degenerative orthopedic disorders, as well as joint pain," she said. "Obesity can lower immune response as well as cause or worsen high blood pressure, several types of cancers, hypothyroidism and cardiovascular disease."

In addition, heavy pets cannot endure heat, are less likely to enjoy exercise and, if surgery is needed, they might not be able to tolerate the anesthesia.

"The only known nutritional modification that we have that will increase longevity and lower the incidence of disease is energy restriction," Irlbeck said. "Serving sizes have increased for people and for dogs often in the form of high-calorie treats."

The Purina PetCare Company in St. Louis recently completed a 15-year study of dogs born from the same litter. One littermate was given a daily serving of dog food and the other dog was given exactly 25 percent less, according to Steve Thompson, director of the Pet Wellness Clinic at the Purdue University School of Veterinary Medicine in West Lafayette, Ind.

"After following them for 15 years the dogs given less food had less hip dysphasia, less veterinary visits and had a better quality of life," Thompson told UPI.

There are no dog and cat weight charts; ideal weight varies by breed, within breeds and in mixed breeds, so how does an owner determine if a pet is overweight?

A veterinarian can tell, but an article on "Canine Obesity" on the IAMS Web site, Eukanuba.com, advises dog owners to look for minimal fat covering the dogs ribs, a waist easily seen from above and the dog's abdomen slightly tucked up when viewed from the side.

"If you can't feel the ribs easily, your dog has no waist and his abdomen drags, he's too fat," the Web site advises.

Many factors contribute to pet obesity, including: overfeeding, inactivity, breed, age and sex, spay/neuter status, diabetes mellitus, hyperadrenocorticism and hypothyroidism, according to IAMS.

A veterinarian should determine that no medical reason is causing the weight gain.

"To lose weight it takes caloric restriction and exercise especially with advancing age as our metabolism slows," Irlbeck said. "We are seeing an older, more geriatric population of animals, as we are of people."

Thompson said a veterinarian will first take a nutrition history and perhaps switch to a lighter pet food, or suggest reducing the amount of pet food initially by 25 percent.

"We tend to have more control over animal diets than ours -- sometimes," Irlbeck said.

However, the IAMS Web site suggests if it is determined a pet needs to lose weight, a family meeting should be called to find out who is feeding the family pet and how often.

With family members often not at home at the same time, misunderstandings can occur and sometimes more than one family member is feeding the pet. Several family members may also be giving the dog or cat high-calorie treats.

"My vet has an owner with a 19-pound Pomeranian and the owner gave her the required amount of diet food, but the dog's heart medication was given in a whole hot dog, twice a day," Irlbeck said. "The owner wondered why the dog wasn't losing weight."

Unlike human diet foods, pet diet foods seem to have a better success rate.

"I can speak for our weight control foods. They do work. But there needs to be portion control and appropriate exercise, too," Carey said. "We include l-carnitine in our dog weight control foods to help burn fat -- and it does. In our Eukanuba Cat Weight Control food, we also include an increased level of vitamin A to both meet the requirement for this essential vitamin and to help avoid weight gain -- this works, too."

It also is advised when a dog finishes eating any remaining food should be removed, because the dog could continue to eat out of boredom. Cats are nibblers and prefer to have dry cat food available all day.

"We should exercise cats, because they used to get exercise hunting when they used to go in and out of doors," Irlbeck said. "Many cats are now trapped indoors and we need to compensate for that -- people do not exercise their pets as much as they should."

Dogs are pack animals and before there were leach laws and dual-income homes leaving dogs alone all day, dogs often ran together in a pack throughout neighborhoods.

"Dogs are social creatures, and they need companionship, if left alone with food available, they'll eat because they are bored," Irlbeck said. "Perhaps we should advise people to get two puppies so that they would have company, they could tear up the house and eat your shoes, but probably not get fat -- most of animal obesity are people-made problems."